Method of operating an electromechanical vehicle braking system

A technology of vehicle braking and wheel brakes, which is applied in the direction of brakes, vehicle components, braking transmissions, etc., and can solve problems such as rear-end collisions and unfavorable extension of braking distances

Active Publication Date: 2019-04-23
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The invention relates to a method of operating an electromechanical vehicle braking system comprising an ESP module and at least two brake circuits each having two wheel brakes each assigned at least one inlet valve and at least one outlet valve, wherein each brake circuit contains at least one high-pressure switching valve and one low-pressure switching valve and at least one low-pressure storage device, wherein the final pre-pressure is at least A part is established according to a trigger factor, wherein closing each inlet valve and opening each outlet valve causes the low pressure reservoir to be filled with a first pre-pressure amount of brake fluid, wherein once the first pre-pressure amount has been reached, the ESP pump is activated for filling A vehicle braking system comprising an adjustable final pre-pressure amount dependent on a factor of a low-pressure storage device, wherein all valves are closed if a set final pre-pressure is reached, and wherein the final pre-pressure built up during the occurrence of a braking procedure is at least partly Or at least one wheel brake supplied to the vehicle braking system is supplemented by an additional pressure which depends at least on the intensity of the braking program, wherein at least the inlet valve is opened and the ESP pump generates the additional pressure.

Application Domain

Braking action transmissionAutomatic initiations

Technology Topic

Automotive engineeringHigh pressure +5


  • Method of operating an electromechanical vehicle braking system


  • Experimental program(1)

Example Embodiment

[0008] It should be pointed out that the features and measures described individually in the following description can be combined with each other in any technically advantageous manner and disclose additional embodiments of the present invention. In addition, the specification describes and illustrates the invention in this regard.
[0009] Therefore, a method of operating such an electromechanical vehicle braking system is described below. The vehicle brake system includes an ESP (Electronic Stability Program) module and at least two brake circuits. Both brake circuits have two wheel brakes. Both wheel brakes are assigned at least one inlet valve and at least one outlet valve. Each brake circuit includes at least one HS valve and at least one US valve and at least one low-pressure storage device. The method according to the invention provides that the final pre-pressure is established in at least part of the vehicle braking system before a possible braking procedure. The term "final pre-pressure" may refer to the pressure preferably established in at least one area of ​​the hydraulic components of the vehicle brake system in this case. The final pre-pressure is not continuously and directly effective from the start during the operation of the vehicle, but is only established based on the trigger factor. For this purpose, it is provided that each inlet valve is closed and each outlet valve leading to the low-pressure storage device is opened so that the low-pressure storage device is filled with the brake fluid in the amount of the first pre-pressure, wherein once the amount of the first pre-pressure is reached, The ESP pump is activated to fill at least a part of the vehicle braking system including the low-pressure storage device. The amount of the final pre-pressure can be adjusted by a factor, wherein if the set amount of the final pre-pressure is reached, all valves are closed.
[0010] If all valves are closed, the amount of final pre-pressure is stored and if it is necessary to engage the wheel brakes accordingly, the final pre-pressure is fully effective for the wheel brakes. For this purpose, it is only necessary to open the inlet valve. The amount of final pre-pressure also in each low-pressure storage device is therefore generated according to the trigger factor which will be mentioned in detail later. When the inlet valve and the optional outlet valve are opened, the amount of final pre-pressure stored in each low-pressure storage device is therefore also effective for the wheel brakes.
[0011] It is provided that the final pre-pressure that has been established before by the pump of the ESP module is supplied to at least one wheel brake of the vehicle braking system during the braking procedure that has already occurred. It is possible to supply all the final pre-pressure or only part of it to the wheel brakes. Alternatively, it is provided that the final pre-pressure can be supplemented by an additional pressure that depends at least on the strength of the braking program. The total pressure resulting from the final pre-pressure and the additional pressure is at least partially supplied to at least one wheel brake in each required amount.
[0012] The resulting advantages show themselves a significant improvement in the efficiency of electromechanical vehicle braking systems operating in this manner. Passing through the ESP module according to one or more trigger factors, in other words the final pre-pressure established by the ESP pump, results in a significant reduction in the reaction time of this type of system. The background to this is the fact that from now on in each case a sufficiently high brake pressure is effective before the potential braking procedure. When the intended braking procedure actually takes place, this sufficiently high braking pressure can then be used directly, completely or only in the required amount, in order to directly affect the wheel brakes. The significantly faster flow of fluid to at least one wheel brake is achieved due to the quasi-direct possibility of obtaining pressure from a system that has been pre-filled with pressure in this way. In this regard, therefore, it is possible to reduce the reaction time of the known electromechanical vehicle braking system to almost zero under ideal conditions.
[0013] The achievable increase in efficiency is higher than the current level of responsiveness of vacuum-based conventional braking systems. This does not matter whether this is a manual input, in other words initiated by the driver's desire and/or autonomous system. The method according to the present invention will be understood as a type of function that can occur in parallel or in combination with existing control functions. As long as the vehicle has corresponding response hardware, it is possible to directly retrofit, for example, an existing vehicle in this way. It is naturally possible to retrofit any vehicle that first requires the installation of corresponding hardware in order to perform the method proposed here.
[0014] Where it is possible to give an indication of a possible imminent braking procedure, one or more actual triggering factors for establishing the pre-pressure can be found. It can be seen from this that the term "trigger factor" is understood to be all indications that make it possible to provide foresight in this direction. Because the improvement in efficiency that can be achieved by the present invention occurs in many fields, there are correspondingly many possible trigger factors for the operation of this type of electromechanical vehicle braking system.
[0015] According to a preferred further development of the basic inventive concept, the first of these triggering factors may exist in the fact that the drive type of each control element is initiated in order to control the motor output as an indication of a possible imminent braking procedure. Even if the control element is, for example, a gas cock or another type of auxiliary device, the measures mentioned here will be explained in detail below using a foot pedal, in other words an accelerator pedal.
[0016] Therefore, it is possible to use the type of releasing the manual accelerator pedal by lifting the foot of the person controlling the vehicle as a basis in order to interrupt the imminent movement procedure. This can be, for example, a significant quick release of the accelerator pedal. This is naturally always necessary if the right foot that normally operates the accelerator pedal is removed from the accelerator pedal as quickly as possible and placed on the brake pedal in order to decelerate the vehicle.
[0017] In practice, the first trigger factor can be defined according to the recognizable rate of change of the accelerator pedal, or through internal calculations of the quick release of the accelerator pedal. Expressed as a function, this can be, for example, as follows:
[0019] In doing so, "Acc_ped_rate_of_change" indicates the rate of change of the accelerator pedal, while "Acc_ped_pos_current" indicates the actual position of the accelerator pedal and "Acc_ped_pos_prev" indicates the previous position of the accelerator pedal. The various time periods to observe this are considered to be "sample_time" and "Acc_ped_rate_thresh" represents the rate of change that is considered to be the rapid release of the accelerator pedal to initiate the braking procedure. Finally, the term "Acc_ped_quick_release" contains the value "0" or "1" to indicate whether the accelerator pedal has been quickly released according to the upcoming braking program or not. The result "0" means that there is no measure, and "1" is used as a trigger to build up the pre-pressure.
[0020] Finally, the functions described here are used to screen the movement of the accelerator pedal in such a way that the release of the accelerator pedal can be considered the start of subsequent driving of the vehicle brake. In fact, this screening process can be set to be extremely sensitive, because the final pre-pressure establishment by the ESP pump only includes preventive measures that initially do not have any direct impact. On the contrary, the level of safety achieved by this function should have such a high level that in each case the braking procedure that is actually about to occur is recognized.
[0021] In order to set the sensitivity level regarding activation through this function, it is preferable that the value of "Acc_ped_rate_thresh" can be set. In addition, the screening can be performed in such a way that the rate of change is calculated over a longer period of time, so as to reduce the influence of switching or possible signal errors in this way.
[0022] Therefore, the function may include, for example, a learning part or may implement the learning function itself. For this purpose, the rate of change; in other words, the various releases of the accelerator pedal can be observed over a longer period of time in such a way as to interrupt whether the customized activation program is actually about to occur with higher accuracy. The purpose is the gradual change of the value related to the sensitivity of the function activation. Due to the learning characteristics of this function, the wider the basis of this value, the more accurate or more precisely the smoother the adjustment.
[0023] The possible signal error of the input signal related to the function may mainly come from the accelerator pedal position signal that measures the respective release rates of the accelerator pedal. Under certain conditions, this can have undesirable offset or accuracy issues at a certain point in time and regarding the release rate of the accelerator pedal. Due to the previously described learning feature of this function, its impact can be reduced or even eliminated accordingly.
[0024] The position of the accelerator pedal and/or the rate of change up to the upper limit and/or the lower limit can naturally also be rounded to be able to provide an additional measure of input to the screening process in this way.
[0025] According to an advantageous further development, the signal of the detection device can be used in order to serve as a second trigger factor for the establishment of the final pre-pressure. It is particularly preferred that the detection device is, for example, a device for object recognition, in other words for obstacle recognition, as provided in the case of a collision warning device of a vehicle. Conventionally, this type of device is an optical system containing, for example, an optical sensor, such as a camera and/or radar, for sensing the environment. Such devices also include all other sensor types used to detect physical obstacles.
[0026] As long as the relevant object is detected by the detection device, the signal provided without the intervention of the person controlling the vehicle can be used to establish the final pre-pressure by the ESP pump. It is sometimes possible according to the present invention to switch the brake into the ready mode in this way very early before the necessary braking action in order to reduce collisions or perform an emergency braking procedure. According to the invention, by means of an advance warning about possible braking actions, the respective necessary pre-pressure has therefore often been effective for a sufficiently long period of time in order to build up its pressure. In particular, in combination with the collision warning device on the vehicle, this produces an efficient braking system whose safety level can be further significantly improved by the method according to the invention.
[0027] The invention is suitable for integration with an automatic parking system in a very advantageous manner. This type of system may be, for example, a fully automatic and/or remotely controlled parking system. When the automatic parking procedure of the vehicle is initiated, it is possible, in particular, that the fact that the value of the external temperature that can be set or established is not reached is used as the third trigger. The background is that the brake fluid present in the hydraulic components of the brake system has a naturally higher viscosity at lower temperatures. Therefore, it is necessary to increase the braking pressure, especially in winter months, in order to be able to provide the required braking behavior, in other words the required braking force.
[0028] According to the present invention, in order to determine the variable magnitude of each final pre-pressure, it is usually possible to use the value of the actual external temperature that has been specifically measured or is available through modules already in the vehicle. The variable size, in other words the dependent factor setting of the final pre-pressure, and the external temperature as a factor of the general setting of the variable final pre-pressure will be described again below by way of example.
[0029] Together with the automatic parking system, sometimes a small effective distance is used to be able to perform parking actions. In doing so, it is more important that this can also be adequately performed in the case of a request for autonomous deceleration usually through the parking system. In other words, the reaction time between the deceleration request and the actual execution should be as short as possible. As explained earlier, this is not necessarily the case especially at low temperatures. Now, for this purpose, the present invention proposes quasi-compensation for the more viscous brake fluid at that time.
[0030] The inventive concept is of course not limited to the use of various universal external temperatures, but also includes, for example, the actual temperature of the brake fluid. According to the invention, in some cases, this can deviate from the external temperature so that this can also be taken into account in the context of the magnitude of the pressure level to be established. In each case, the external temperature and/or the actual temperature of the brake fluid can therefore be used as a third trigger for the establishment of the pre-pressure. In this way, at least a lighter pre-pressure of the brake system is ideal in order to sufficiently offset the higher viscosity of the brake fluid. The respective magnitude of the pressure level may depend, for example, on the type of brake fluid and/or the external temperature.
[0031] It is generally explained at this point that the possible braking procedures identified within the scope of the present invention can be implemented in many ways. In particular, refer to the possibility of manual, in other words actuation of the brake pedal and/or deceleration request according to the autonomous decision of the vehicle system. In this way, according to the advantages of the present invention, it can be used by all forms of deceleration requests regarding their origin and/or trigger.
[0032] According to a preferred further development of the present invention, the establishment of the final pre-pressure can occur in two stages, as already indicated above. This means that the final pre-pressure can initially reach the initial size, in other words the first pre-pressure value, and can subsequently be increased, for example, to the final size, in other words to the respective selected final pre-pressure. This type of two-stage pressure buildup is considered to be particularly advantageous in combination with the first and/or second trigger factor. In this context, because the vehicle can move at a significantly higher speed than in the case of automatic parking. In this regard, it can be assumed that the required pre-pressure is correspondingly higher in order to achieve a sufficient braking effect.
[0033] It can be provided that, for example, brake pads or brake shoes are moved as close as possible to the corresponding brake assembly. These mentioned brake components can be, for example, brake discs or brake drums. A quasi-compensation of the possibly increased viscosity of the brake fluid that can occur in the case of low external temperatures is thus also possible.
[0034] The present invention further provides that the brake system operated in this way includes valve devices, in other words HS valve (HSV = high pressure switching valve), low pressure switching valve (which can also be described as a pilot valve US valve), and inlet and outlet The valve device is connected upstream of each wheel brake. These valve devices may be of the type of shut-off valves or preferably flow valves, especially pressure delivery valves and/or "TMC shut-off valves" (TMC = dual chamber brake master cylinder). Some of these valve devices have the advantage that the brake fluid can pass in a progressively reduced manner. In each case, at least the inlet valve should be adapted to transmit the required amount of pressure effective at the input of said inlet valve to its output and therefore to the wheel brakes when open.
[0035] The initial pre-pressure, in other words, the first pre-pressure value can therefore add up, for example precisely or approximately or up to 0.3-3 bar, preferably 1-3 bar. Subsequently, the final pre-pressure can be further increased using an ESP pump, for example to 3-30 bar and thus to the final size. In this way, sufficient pre-pressure is effective in the braking system and this can then be directly at least partially transmitted to at least one wheel brake when needed. For this purpose, in the case of an effective pre-pressure, the valve device can be at least partially opened during the braking procedure, wherein the amount of pressure stored in the low-pressure storage device is also effective.
[0036] Therefore, the braking system is filled with a pre-pressure that has sometimes been established according to the first and/or second trigger factor before a possible braking action, and then said pre-pressure is almost directly effective as needed in the case of a deceleration event. Fundamentally mentioned at this point, the present invention understands that the term "final pre-pressure/pre-pressure" used refers to the initial pre-pressure and also refers to the final pre-pressure. In other words, in this case, the term "final pre-pressure" is used as the general term for its initial and final pressure, and the term "pre-pressure" is also occasionally used.
[0037] It is advantageous to select the highest possible final pre-pressure in relation to sufficient brake output during the imminent braking action. However, the pre-pressure is established by the ESP pump when the inlet valve is closed, so that the establishment of the pre-pressure does not initially have any significant impact, and there are only beneficial and high preventive pre-pressures that can be directly invoked as needed. It is possible in the system.
[0038] A further advantageous embodiment of the basic inventive concept contains the pre-pressure, in other words the possible dependence of the respective magnitude of the initial first pre-pressure and the final pre-pressure from the possible factors still described. In addition or as an alternative, the present invention provides this type of dependency for various time periods during which the pre-pressure is maintained. Possible dependencies can take effect, for example, with regard to relevant external conditions.
[0039] A further possibility for this type of dependence is to consider the windshield wiper device on the vehicle. This equipment often contains windshield wipers, which are used in combination with windshield washing water to clean the windshield or remove any water, such as possible rainwater located on the windshield area of ​​the vehicle. In particular, the latter variant is interpreted as an indication that the road on which the vehicle is traveling may also be wetted by rain. Therefore, this information can be used to adjust the size of the pre-pressure, such as the final pre-pressure, to suit various road conditions. Therefore, in the case of rain, it is assumed that the static friction of the wheels on the road will generally decrease, so that the high braking effect that occurs in a short period of time can quickly cause the wheels that have been decelerated in this way to become locked. In contrast to dry weather conditions, the magnitude of each pre-pressure can be smaller in order to consider the conditions accordingly.
[0040] It is also possible to consider the possible operating positions of the windshield wiper device in this respect. First of all, the speed of the windshield wiper is related, and the speed can be, for example, fast or slow. It is possible to derive information about possible road conditions from the speed information in a simple manner. Therefore, it is judged that the road is unsafe from the fast operation, not in the case of only slow operation. The goal is to achieve braking efficiency in a customized system in an ideal way. For this purpose, the length of the time period for maintaining and/or establishing each pre-pressure is preferably kept variable and can be adjusted depending on the factor. This applies correspondingly to matching the respective magnitude of the pre-pressure. The preferred automatic setting of the various values ​​can be performed, for example, according to the vehicle and further various embodiments. It is possible to access the stored or calculable limit values ​​corresponding to each situation.
[0041] The previously described adjustability can be achieved in an advantageous manner also naturally depending on the individual external temperature. It is possible to also consider the different magnitudes of the hardness of the vehicle tires depending on the external temperature, for example. In this case, it is feasible to use the detected system voltage of the vehicle. Each actual system voltage can affect whether and/or how high the available support is, without negatively affecting and/or damaging other devices and functions of the vehicle. In the case that the system voltage is in the lower limit range, it is possible to use the function or not to use it, and the vehicle braking system and the generation of the necessary pre-pressure naturally have absolute priority. For example, when the system voltage is 6.0 volts, this function is not available. In contrast, the best efficiency of this function should be available when the system voltage is 13.0 volts.
[0042] In addition, the present invention provides that the adjustability can also be achieved based on other unfavorable conditions detected, for example, by an optical system that has been provided or specially allocated. In doing so, it is possible to consider those conditions regarding the various road surfaces that can have a negative impact on the braking behavior of the vehicle. Therefore, it is feasible to recognize that the road surface is poor and this can provide information about the road surface on which the vehicle is traveling, for example. Severe road conditions, such as uneven areas that distinguish between reinforced and non-reinforced parts, can therefore equally support the setting of the entry time period during the pre-filling period and the pre-filling pressurization period. This type of measure contributes to the further development of the inventive concept in an advantageous way the effect that the achievable efficiency improvement is further increased and therefore the person controlling the vehicle has more trust in the vehicle and the overall stability of the vehicle is improved.
[0043] Factors based on the respective gear ratio and/or the yaw rate of the vehicle can also be used for the adjustability. The functions described here can naturally also be restricted to be effective only when a specific value of vehicle speed is exceeded. This value can be different depending on the activation conditions of the pre-pressure establishment. For example, it is feasible that the vehicle speed is very low or even no vehicle speed is observed during the automatic parking procedure (third trigger factor). In contrast to this, the combination of this function with the first and/or second trigger factor may rely on the fact that the function is only effective when the vehicle speed exceeds, for example, 90 km/h. The effectiveness of this function can also be limited to a range of, for example, 90km/h to 120km/h.
[0044] Considering the time period discussed earlier, the present invention preferably provides the following measures:
[0045] As soon as the condition of the first trigger factor becomes effective, the electric motor, in other words, the use function of the ESP pump can start. This can, for example, use slow rotation to establish a first pre-pressure during the initial period of time when pre-filling occurs. The initial pre-pressure can be maintained, for example, for an initial period of time where the pre-filling occurs precisely or approximately or up to 5.0 seconds. The initial pre-pressure may have a value of, for example, accurate or approximately or up to 3.0 bar. In the case of a shut-off valve device, this function continues to use an electric motor, in other words an ESP pump, in order to establish a final pre-pressure that is fundamentally preferably alternatively adjustable in a factor-dependent manner and can be, for example, 3 bar to 30.0 bar. The final pre-pressure obtained can then be maintained, for example, for the duration of time that the pre-filling takes place and the time period can total to be precise or approximately or up to another 5.0 seconds.
[0046] As long as it is recognized that the brake pedal has been activated within the time period when the pre-fill pressure occurs and therefore the driver has actively requested the vehicle to decelerate, the braking system can begin to provide the requested deceleration level.
[0047] If the brake pedal is not activated and the brake system is pre-filled to the final pre-pressure and exceeds the duration of the pre-fill pressure, the function can start the reduction of the pre-pressure. This reduction process can continue, for example, until the initial pressure level has been reached. In addition, in the event that the brake pedal is not driven further, it is possible for this function to start the cycle of establishing the build pressure of the final pre-pressure from this point in time and maintain it for the duration of the occurrence of the pre-fill pressure.
[0048] It goes without saying that the brake pedal used in the previous specification can naturally also be provided by a different brake device.
[0049] Regarding the second trigger factor, in the presence of the second trigger factor, it is possible for the function to start the pressure build-up as described in the previous first trigger factor. However, other values ​​can be provided for various pre-pressure and various time periods during the pre-filling of the brake system. Therefore, it is possible to adjust the time period that occurs to adapt to the pre-pressure and fill the pre-pressure based on factors such as the general effectiveness of the effective collision warning program and the autonomous braking program through the vehicle. Therefore, it is possible to tailor the efficiency level of the braking system in an advantageous manner to suit each condition.
[0050] Regarding the aforementioned measures, the present invention provides some basic possibilities for further development, as explained below:
[0051] Therefore, in the process of establishing the pre-pressure; in other words, in the case of an active function, for example, when the brake pedal or the accelerator pedal is actively driven, it is possible to request an autonomous deceleration to reset the counter of each time period when the pre-fill pressure occurs. of. In other words, each deceleration process starts the establishment of the pre-pressure from zero time.
[0052] In order to prevent possible continuous operation of the function in all types of operations valid for the function, the function may be reset, for example, after a defined period of time for its continuous operation. In this respect, the various magnitudes of the pre-pressure that may be effective will be reduced again.
[0053] Depending on the system voltage and/or external temperature, the effectiveness of this function can also be changed in this regard, as each mode is effective for different temperatures and/or voltage ranges. Therefore, for example, the automatic parking operation may be effective at a temperature lower than the temperature at which the driver inputs the deceleration request operation (first trigger factor).
[0054] In addition, the effectiveness of the various modes of operation can also be adjusted according to the error status of available sensor elements or other vehicle modules. Therefore, in the case of an autonomous deceleration request (second trigger factor), the conditions for the validity of the corresponding mode can be in the mode in which the driver inputs the deceleration request if the detection device intended to provide advance warning of a forward collision is in a malfunction state Use it in a way that is effective and remains effective in every situation. Therefore, the various modes can be used in an advantageous manner in order to provide a further reduction in reaction time by the corresponding safety device. In this way, it is possible to compensate, at least in part, for the possible effects of, for example, the failure of the on-board system.
[0055] In general, the various modes of operation should be effective regardless of any steering input on the component by the person controlling the vehicle or by the autonomous control source. However, the possible intervention of the stability control function or the anti-lock function may cause the function to be reset.
[0056] In general, the establishment of the pre-fill pressure according to the present invention may also improve the efficiency of the driver's input to the ESP and/or RSC module (roll stability control). This especially also occurs at low temperatures. In each case, the function now proposed significantly improves the efficiency in the case of a person controlling the vehicle or a braking action performed by autonomous intervention. In addition, the conditions for executing the automatic parking procedure are significantly improved, especially in low temperature conditions.
[0057] As a factor for determining the magnitude of the adjustable final pre-pressure, it is possible to use, for example, the temperature, in other words the actual external temperature and/or the actual temperature of the brake fluid, the vehicle speed, and the value of wheel slip such as wheels of the non-transaxle. of. For example, if an automatic emergency braking program is detected with a small amount of wheel slip and an external temperature greater than 0°C, a final pre-pressure amount of 15-30 bar can be set. On the other hand, if the automatic emergency braking program is detected in the case of a large amount of wheel slip and the external temperature is less than -25°C, a final pre-pressure amount of 5 bar can be set.
[0058] The present invention uses an ESP module, in other words, an ESP pump, to generate a factor-dependent adjustable final pre-pressure in the vehicle braking system. The final pre-pressure is immediately effective so that the braking distance is significantly reduced, which is suitable for driver-induced Braking application (manual braking) and automatic braking events (automatic parking program; automatic emergency braking). For example, in the case of manual braking events, automatic emergency braking, automatic parking procedures, remotely controlled automatic parking procedures, and/or driving, the pressure reduction is achieved through an adjustable final pre-pressure for a short braking distance. set up.


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